Selective use of solvent components in solvent dewaxing



Aug. 28, 1956 L. J. FORD SELECTIVE USE oF soLvENT COMPONENTS 1N soLvENTDEWAXING Filed Dec. 7, 1951 United States Patent SELECTIV E USE FSOLVENT COMPONENTS IN SOLVENT DEWAXIN G Lloyd J. Ford, Baton Rouge, La.,assignor to Esso Research and Engineering Company, a corporation ofDelaware Application December 7, 1951, Serial No. 260,421

3 Claims. (Cl. 196-18) The present invention is concerne-d with animproved process for the removal of waxy constituents from mineral oilscontaining the same. The invention is more particularly concerned with adewaxing operation utilizing two solvents, one of which comprises ananti-wax solvent while the other of which comprises an oil solvent. Thepresent invention is particularly concerned with the use of a solventmixture in a dewaxing operation comprising a ketone and an aromatic asfor example toluene in order to increase dewaxed oil yields and lteringrates. In accordance with the present invention the anti-wax solvent asfor example the ketone is incrementally added to the waxy oil during thechilling cycle while the solvent having a solubility for oil is added tothe chilled waxy oil in toto at the filtering temperature.

In the rening of hydrocarbon oils such as petroleum oils, it is known tosegregate paraffin waxes from socalled paran distillates, waxy lubes andthe like. The segregation of these waxes is secured by a number ofprocesses. For example, it is known to chill the selected wax containingoi-l fraction in order to secure crystallization of the wax and then tofilter or centrifuge the wax crystals from the oil. It is also known touse various dewaxing solvents such as liquid normally gaseoushydrocarbons, such as propane, as well as, other solvents such asmethyl-ethyl ketone and the like. In these dewaxing operations, it isalso known to use various filter aids and other agents in order torender the dewaxing and filtering operations more efficient. The waxsegregated from the hydrocarbon oil, usually termed slack wax containsfrom `about to 40% of oil. The oil content and melting point range ofthis wax maybe reduced if desirable by means of a distillationoperation. The slack wax is then handled usually by sweating in a mannerto reduce the oil content to less than about 4% by weight. This, crudescale wax, generally has -an oil content of about 2.5% by weight. Inorder to remove this oil from the wax and to produce a rened wax havingan oil content below about .5%, usually below about .3% various pro-lcedures have been proposed and employed.

As pointed out, it is known to employ solvent mixtures wherein onesolvent comprises an anti-wax solvent while the other comprises asolvent having a solubility for oil. A solvent mixture of this characterfor example comprises 60% by volume of methyl-ethyl ketone and 40% byvolume of toluene. When utilizing a mixture of this character it hasbeen the practice to add the mixture incrementally to the waxydistillate as it is being chilled. However, t has now been discoveredthat unexpected desirable results are secured providing the anti-waxsolvent is added incrementally and the solvent having a solubility foroily constituents is added in toto at or near the filtering temperature.The process of the present invention may be more readily understood byreference to the drawing illustrating one embodiment of the same.

Referring specically to the drawing, a waxy distillate is introducedinto the system by means of feed line 1. The waxy distillate flowsserially through chilling zones 2, 3, 4 and 5 wherein the temperature ofthe waxy distillate is progressively reduced. A typical operation is tointroduce the feed oil into the initial chilling zone at a temperatureof about 130 F.; to introduce the feed oil into the second chilling zoneat a temperature of about F.; to introduce the waxy distillate to thethird chilling zone at a temperature of about 60 F.; to introduce thefeed oil to the fourth chilling zone a temperature of about 25 F. and tochill the same in the fourth chilling zone to a liltering temperature inthe range of from about -10 to }-10 F. The number of the respectivechilling zones as well as their arrangement may be varied appreciablyand either direct or indirect chilling means utilized. For purposes ofillustration it is assumed that the anti-wax solvent comprisesmethyl-ethyl ketone and that the aromatic solvent having a highsolubility for oil comprises toluene. It is also assumed that 3% volumesof total solvent mixture is utilized per volume of waxy oil beingdewaxed. The solvent mixture comprises 60% by volume of methyl-ethylketone and 40% by volumev of toluene.

The methyl-ethyl ketone is introduced into the system. by means of line6, and at least a portion of the salmeA passed serially through chillingzones 7, 8, 9 and 10. The: methyl-ethyl ketone in zone 7 is chilled to atemperature: corresponding to the temperature of the waxy distillate: Aportion of the methyl-ethyl.

removed from zone 2. ketone is added to the waxy distillate by means ofline 11 while the remainder is chilled in zone S to a temperatureapproximating the temperature of the chilled distillate removed fromzone 3. A portion of the methylethyl ketone removed from zone 8 is addedto the waxy distillate removed from zone 3 by means of line 12. Theremainder of the methyl-ethyl ketone is further chilled in zone 9 to atemperature approximating the temperature of the distillate removed fromzone 4. Another portion of the methyl-ethyl ketone removed from zone 9is added to the distillate removed from zone 4 by means of line 13. Theremainder of the methyl-ethyl ketone is chilled in Zone 10 to atemperature approximating the temperature of the waxy ydistillateremoved from zone 5 and added to the waxy distillate by means of line14.

The toluene in accordance with the present invention is introduced intothe system by means of line i5, chilled in zone 16 to a temperatureapproximating the temperature of the cold distillate removed from zone 5and added to the distillate by means of line 17. The entire mixturecomprising oily constituents, crystallized wax constituents, toluene andmethyl-ethyl ketone is held at this ltering temperature and passed toliltering zone 18 wherein the solid wax particles are segregated fromthe oily constituents by any suitable filtering or separation means. The:filtering zone may comprise plate and frame presses, centrifuges orequivalent suitable equipment for the scparation of the precipitatedwaxy constituents from the oily constituents. The oil and a portion ofthe solvent is removed from zone 18 by means of line 19 and the wax cakewashed with a wash solvent introduced into filtering zone 18 by means ofline 20. Slack wax Kand solvent are removed from zone 18 by means ofline 21 and passed to a distillation zone'22 wherein'a separation ismade between the waxy particles and the solvent, lt is to beunderstoodnthat other means of separating the solvent from the wax maybe utilized if desirable. The wax substantially free of solvent isremoved from separation zone 22 by means of line 23 and furtherrened asdesired. The solvent mixture comprising methyl-ethyl ketone and tolueneis removed overhead from zone 22 by means of line 24 and passed todistillation zone 25.

The oil-solvent mixture removed from filtering zone 18 by means of line19 is introduced into distillation zone 26 wherein a separation is madebetween the oily constit uents and the solvent mixture. The oil isremoved from Zone 26 by means of line 27 while the solvent mixture isremoved overhead by means of line 2S and passed to distillation zone 25.A separation is made in zone 25, which may comprise a distillation zone,between methylethyl ketone which is removed overhead by means of line 29and the toluene which is removed as a bottoms stream by means of line30. It is to be understood that ltering zone 18, distillation zones 22,2S and 26 may comprise any suitable number and arrangement of stages.

The methyl-ethyl ketone removed by means line is preferably recycled tothe system and added in increments to fresh, waxy distillate while thetoluene is rccyoled and `added in toto at or near the lteringtemperature by means of line 17. Fresh methyl-ethyl ketone and toluenemay be added as required.

The invention is broadly concerned with a dew ine operation utilizingtwo solvents, one ot which is characterized by being an anti-waxsolvent, while the other is characterized by having a relatively highsolubility for oily constituents. Solvents of the anti-waxcharacteristic, for example, comprise methyl-ethyl ketone, methyl-propylketone, acetone and the like, while solvents having a relatively highsolubility for oily constituents comprise benzene, toluene and otheraromatic solvents. The invention is specically directed to a processwherein the `anti-wax solvent is incrementally added to the waxydistillate it is being chilled to a filtering temperature, while thearomatic solvent is added in toto at or near the filtering temperature.The method of `adding the anti-wax solvent inay be varied appreciably.lt may be added in increments of from two to six and the quantity addedas each increment varied appreciably. The amount added at each incrementmay be equal in volume, or a relatively small amount may be initiallyadded and relativeiy larger amounts added in succeeding stages. Forinstance, a very satisfactory method of operation is to employ tivechilling stages and to use Iabout 350 volumes of a solvent mixture,comprising 60% by volume of methyi-ethyl ketone and 40% by volume oftoluene, per 100 volumes of waxy oil being dewaxed. Under theseconditions 30 volumes of methyl-ethyl ketone is added in the rstchilling stage, 30 volumes in the second chilling stage, 60 volumes inthe third chilling stage, 90 volumes in the fourth chilling stage and140 volumes of toluene added at the iltering "-2 temperature.

The process of the present invention may be more fully `appreciated bythe following example illustrating the same:

Example Operation Operation I II Filtration Rate., Gal/Hr./Sq. FtDewaxed Oil Yield Dewaxed Oil Inspections:

Pour, F Cloud, F

From the above it is apparent that filtering rates are materiallyincreased as well as dewaxed oil yields.

General operating conditions may be varied appreciably. For example, theconcentration of the anti-wax solvent may vary from about 50% to 70% byvolume while the concentration of the oil solvent may vary from 50% to30% by volume. The amount of solvent mixture utilized may vary fromabout .5 to 8 volumes per volume of oil being dewaxed. Preferred ratiosare from 3 to 5 volumes of solvent mixture per volume of oil beingdewaxed. ln accordance with the present invention, it is also preferredthat the temperature of the oil solvent approximate the lteringtemperature of the cold waxy distillate. In no instance should thetemperature of the oil solvent added to the cold waxy distillate varygreater than about l0-20 degrees.

What is claimed is:

l. The process for the removal of waxy constituents from a a waxy oilcontaining same by the use of two different solvents, a ketone anti-waxsolvent and an aromatic oil solvent, comprising the steps of chillingsaid waxy oil, adding suicient ketone anti-wax solvent of substantiallythe same temperature to said waxy oil to precipitate only a portion ofsaid waxy constituents, subsequently further chilling the resultingmixture of waxy oil, precipitated waxy constituents, and ketone anti-waxsolvent to a lower temperature, subsequently adding additional ketoneanti-Wax solvent of substantially the same temperature as thefurther-chilled mixture to said furtherohilled mixture to furtherprecipitate said waxy constituents from said oil, adding to theresulting mixture subsequent to the addition of all the ketone anti-waxsolvent to be introduced all of said aromatic oil solvent, said aromaticoil solvent being introduced at substantially the same temperature asthe mixture to which it is added, and separating the precipitated waxyconstituents at substantially the same temperature as said aromatic oilsolvent from the resulting mixture of oil, aromatic oil solvent, andketone anti-wax solvent.

2. The process according to claim l wherein said antiwax solvent ismethyl-ethyl ketone and wherein said oil solvent is toluene.

3. The process according to claim 2 wherein from 50- 70 volumes ofmethyl-ethyl ketone are utilized per 30-50 volumes of toluene andwherein from 2-8 volumes of solvent mixture are utilized per volume ofwaxy oil being dewaxed.

References Cited in the tile of this patent UNITED STATES PATENTS2,229,658 Jenkins Jan. 28, 1941 2,274,223 Tuttle Feb. 24, 1942 2,322,438Henry et al. .lune 22, 1943 2,342,798 Fischer Feb. 29, 1944 2,397,868Jenkins Apr. 2, i946 2,463,845 Backlund et al. Mar. 8, i949 m nas...

1. THE PROCESS FOR THE REMOVAL OF WAXY CONSTITUENTS FROM A WAXY OILCONTAINING SAME BY THE USE OF TWO DIFFERENT SOLVENTS, A KETONE ANTI-WAXSOLVENT AND AN AROMATIC OIL SOLVENT, COMPRISING THE STEPS OF CHILLINGSAID WAXY OIL, ADDING SUFFICIENT KETONE ANTI-WAX SOLVENT OFSUBSTANTIALLY THE SAME TEMPERATURE TO SAID WAXY OIL TO PRECIPITATE ONLYA PORTION OF SAID WAXY CONSTITUENTS, SUBSEQUENTLY FURTHER CHILLING THERESULTING MIXTURE OF WAXY OIL, PRECIPITATED WAXY CONSTITUENTS, ANDKETONE ANTI-WAX SOLVENT TO A LOWER TEMPERATURE, SUBSEQUENTLY ADDINGADDITIONAL KETONE ANTI-WAX SOLVENT OF SUBSTANTIALLY THE SAME TEMPERATUREAS THE FURTHER-CHILLED MIXTURE TO SAID FURTHERCHILLED MIXTURE TO FURTHERPRECIPITATE SAID WAXY CONSTITUENTS FROM SAID OIL, ADDING TO THERESULTING MIXTURE SUBSEQUENT TO THE ADDITION OF ALL THE KETONE ANTI-WAXSOLVENT TO BE INTRODUCED ALL OF SAID AROMATIC OIL SOLVENT, SAID AROMATICOIL SOLVENT BEING INTRODUCED AT SUBSTANTIALLY THE SAME TEMPERATURE ASTHE MIXTURE TO WHICH IT IS ADDED, AND SEPARATING THE PRECIPITATED WAXYCONSTITUENTS AT SUBSTANTIALLY THE SAME TEMPERATURE AS SAID AROMATIC OILSOLVENT FROM THE RESULTING MIXTURE OF OIL, AROMATIC OIL SOLVENT ANDKETONE ANIT-WAX SOLVENT.